Many structures, such as residential homes and low rise buildings, are constructed on foundations that are not in direct contact with a stable load bearing underground stratum, such as, for example, bedrock. These foundations are typically concrete slabs. Alternative structures for these foundations are comprised of a footing upon which a foundation wall rests. The footing is generally wider than the foundation wall in order to distribute the structure's weight over a greater surface area of load bearing earth. Therefore, the stability of these structures depends upon the stability of the ground underneath or supporting the foundation. With time, the stability of the underlying soil may change for many reasons, such as changes in the water table, soil compaction, ground movement, or the like. When the stability of the support ground changes, many times the foundation will move or settle. The settling of a structure's foundation can cause structural damage reducing the value of the structure or total property. Inventors have recognized the foundation-settling problem and have developed various devices and methods to correct its effects.
One common device and method to correct foundation settling consists of employing hydraulic jacks in conjunction with piers to lift the foundation. Piers, also known as piles or pilings, are driven into the ground by hydraulic mechanisms until the pier reaches bedrock or until the pier's frictional resistance equals the compression weight of the structure. Once these piers are secured in a stable underground stratum or several stable underground strata, further lifting by the hydraulic jacks raises the level of the foundation. When the foundation is raised to the desired level, the piers are permanently secured to the foundation. The hydraulic jacks are then removed. This method of correcting the level of a foundation generally requires the excavation of a hole adjacent to or underneath the foundation in order to position and operate the lifting equipment.
Foundation lifting devices are well known and exist in many varieties. Methods and devices that lift and support concrete structures are disclosed in three patents issued to the present inventor. In May, U.S. Pat. No. 4,634,319, the present inventor disclosed a method for lifting a structure that requires two separate hydraulic lifting assemblies. A bracket is secured to the building foundation. A hydraulic driving assembly is secured to the bracket to drive a pier into the ground. Once the pier is driven to the desired underground strata, the hydraulic driving assembly is removed. A hydraulic lifting assembly is then placed between the driven pier and the building foundation. The hydraulic lifting assembly then lifts the building foundation to the desired level. Once the foundation is raised to the desired level, a series of adjustable rods are extended down from the bracket to a footer that rests on the pier. When the foundation is secured at that level to the pier, the hydraulic lifting assembly is removed. The device disclosed in this patent is designed to function on the peripheral edge of the foundation.
In the patent issued to May, U.S. Pat. No. 4,800,700, the present inventor disclosed a device and method for lifting concrete slabs. This method comprised the steps of: 1) cutting an access hole in the concrete slab, 2) inserting a lift plate up against the underside of the slab, 3) driving a pier through the access hole through the ground to bedrock or other load bearing strata with a hydraulic driving assembly, 4) removing the hydraulic driving assembly and attaching a hydraulic lifting assembly to the pier and the slab, 5) lifting the slab to the desired height, and 6) securing the pier to the slab and removing the hydraulic lifting assembly. As with the U.S. Pat. No. 4,634,519, this patent requires two hydraulic jacks to complete the process of lifting a concrete foundation or slab. The device and method for lifting a concrete slab is different from the devices and methods used to lift the foundation of a building. This device used to lift a concrete slab is designed to function not on a peripheral edge of the slab, but within an interior portion of the slab.
An additional apparatus for lifting structures is disclosed in May, U.S. Pat. No. 4,854,782. This patent teaches a device and method for lifting a structure that requires two separate hydraulic lifting assemblies. The primary difference between the device taught by this patent and that of the May U.S. Pat. No. 4,634,319 lies in the structure that secures the pier to the foundation. In the U.S. Pat. No. 4,854,782, the pier is supported within a sleeve that is directly secured to the bracket. This structure reduced the number of components that are required to secure a pier to a building from the number used in the U.S. Pat. No. 4,634,319.
Ortiz, U.S. Pat. No. 5,492,437, teaches a lifting device that is made of one or more power cylinders that are pivotally linked to a pier and to a foundation bracket assembly. The pivotal linkage results in self-alignment between the longitudinal axis of the pier and the axis along which compressive pressure is applied to the pier. This patent requires the pier to be lifted above the bracket in order to position the pier within the bracket.
West et al., U.S. Pat. No. 5,246,311, discloses a pier driver having a pair of opposing first upright members straddling a pier support. The upright members are temporarily attached to the foundation and a pair of opposing first foot members operably extending beneath the foundation. A plurality of secondary lifting mechanisms, in cooperation with the piers previously installed by the pier driver, are adapted to lift the foundation. The pier supports of the pier heads are then permanently fixed to the respective piers with a bracket to provide permanent support to the foundation. This patent requires the pier to be lifted above the bracket in order to position the pier within the bracket.
Bellemare, U.S. Pat. No. 5,253,958, describes a device for driving stakes into the ground, particularly a foundation stake used for stabilizing, raising, and shoring foundations. The device disclosed has two rods secured to two hydraulic jacks, the hydraulic jacks and the rods being parallel to the driving axis of the stake. A driving member with a hammering head is provided to drive the stake into the ground. This patent requires that the pier to be lifted above the bracket in order to position the pier within the bracket.
One common feature of the present state of the art is the fact that the pier must be lifted above the bracket that secures the pier to the foundation. This design feature places a significant constraint on the length of piers used. The distance between the top of the bracket and the bottom of the hydraulic cylinder at its maximum position of extension is the maximum permissible length for a pier section that may be used with the device. It may therefore be necessary to use multiple lengths of pipe coupled together in order to form a pier long enough to reach bedrock. Where one pier section is not long enough to reach bedrock, one pier section is inserted within the hydraulic driving assembly and driven into the ground. A drive tool may then be inserted between the pier and the hydraulic cylinder to further drive the pier into the ground. The hydraulic cylinder is then retracted and an additional pier section is placed within the device and coupled to the first pier. The coupled pier is then driven further into the ground. This process is repeated until the pier reaches bedrock.
The shorter the distance between the top of the bracket and the bottom of the hydraulic cylinder at its maximum position of extension, the more pier sections are required to form a pier that reaches bedrock. It is not possible to weld the pier sections together due to the strong possibility that such a process would ignite methane gas trapped within the ground. Therefore, differing non flammable methods of coupling are used. While these couplings are structurally sound, they are not as sound as a pier formed from a single section of pipe that has no couplings. It is therefore desirable to use the longest length of piers possible to reduce the number of pier sections and couplings to limit the chance of mechanical failure.
The present invention is directed toward a device that enables longer sections of piers to be driven into the ground than is disclosed by the present state of the art.